Federal agents in Denver arrested six pimps and rescued nine children they are accused of prostituting during a three-day, nationwide sweep aimed to curb child sex trafficking and underage prostitution.

The Denver children were among 105 recovered in 76 cities throughout the country, the FBI announced Monday. At least 150 pimps nationwide face state and federal charges as a result of the operation.

The Denver FBI division — which includes Colorado and Wyoming — ranked fourth for the number of arrests, behind San Francisco, Detroit and Milwaukee. Details about those charged locally were not immediately available.

"It was a hugely successful weekend for the Denver metro area," Denver FBI spokesman Dave Joly said. "This problem does exist, and it does exist in the metro area."

Police and federal agents usually target truck stops, casinos and websites that advertise dating or escort services as part of their probes, the FBI said in a news release. Arrests for violations of local and state laws often uncover more organized efforts to prostitute women and children.